1. Field of the Invention
The present invention relates to a thin film transistor and a manufacturing method thereof, and more particularly, to the manufacturing method of the thin film transistor with performing a photoresist ashing process to reduce the channel length and to the thin film transistor manufactured by this method.
2. Description of the Prior Art
Thin film transistor (TFT) has been widely applied in the active matrix flat display panel such as the active liquid crystal display panel or the active organic light-emitting diode display panel, wherein the thin film transistor is used as the active device for driving the pixel structure of the display panel. In order to shrink the size of the thin film transistor, the oxide semiconductor materials with high electron mobility have been developed to replace silicon as the material of the channel of the thin film transistor. The oxide semiconductor materials are sensitive to moisture, oxygen and etching solutions, and moisture, oxygen and etching solutions tend to react with the oxide semiconductor materials and thus affect the device characteristics. Accordingly, an etch stop layer is normally formed on the oxide semiconductor material in conventional thin film transistors so that the characteristics of the oxide semiconductor material will not be affected easily, and the thin film transistor with stable device characteristics can be obtained. Therefore, two contact holes in the etch stop layer are required for electrically connecting the oxide semiconductor material to the source electrode and the drain electrode, and the channel length is determined by the distance between the contact holes.
In the conventional manufacturing method of the thin film transistor, the contact holes in the etch stop layer are formed by the lithography and the etching processes, and the distance between the contact holes is limited by the exposure limit of the exposure apparatus. Therefore, the channel length is also limited by the exposure limit of the exposure apparatus, which limits the performance of the thin film transistor.